


On Sibling Rivalry

by tristesses



Category: Sherlock (TV)
Genre: F/M, Genderswap, Incest, Recreational Drug Use
Language: English
Status: Completed
Published: 2012-01-03
Updated: 2012-01-03
Packaged: 2017-10-28 20:45:13
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,589
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/312014
Author URL: https://archiveofourown.org/users/tristesses/pseuds/tristesses
Summary: <blockquote class="userstuff">
              <p>Sherlock mustn't be allowed to continue on like this - drugs and detective work are ruining her. Mycroft intends to stop her. It doesn't go as planned.</p>
            </blockquote>





	On Sibling Rivalry

**Author's Note:**

> For sherlockbbc_fic: _Since we're finally getting some Mycroft/Sherlock fills up in here, I want to up the stakes in the bad/wrong/pleasegodsomeonewritethis: Mycroft/Girl!Sherlock. Anything, idek. Just make it sexy_. Originally posted on 10/18/2010.
> 
> I want to emphasize that Sherlock here is high on cocaine, and therefore this could be interpreted as dub-con, though I didn't think it merited an archive warning. Please read at your own discretion.

The sight of Sherlock being forced to wait patiently like a good little sister while he finishes his conversation with a contentious oil magnate is almost enough to make up for the man's utterly transparent attempts at blackmail. With a sigh, Mycroft leans back in his chair, examines his nails - he misses the days when the Saudis constituted a real threat, something to pay attention to - and glances at his sister. She's slouched against the wall, tarted up in an outfit that would perhaps look attractive on another woman but, when combined with Sherlock's arrogance, sneer, and gawkiness, is more ridiculous than anything. Mycroft must admit, though, that the façade is a good one; she could pass for a normal girl out clubbing, rather than the undercover freelance detective she is. A more thorough look, however, makes him reconsider: her face is flushed slightly, a sheen of sweat on her cheeks and forehead, dried blood crusted around the rim of her nostrils (hastily wiped away, but she didn't do the job completely). No telltale white powder, he has to give her credit for that. Perhaps she _has_ been out at the clubs, as foreign a setting as it may seem for Sherlock.

Mycroft ends his conversation with the oil magnate on a note of thinly veiled malice disguised by typical British politeness, and sets the phone back on its cradle. Sherlock moves as if to speak, and Mycroft pulls out his mobile just to hear her huff in annoyance; naturally, he could multitask, but their sibling rivalry rather forbids him from doing so.

Besides, he is _infuriated_ with her. (The exorbitant use of her alloted funds - alone, not such a hardship, nor if used for her little detective business, but the drugs are quite another story.) So he types a quick text to his Assistant, whose usefulness is quickly meriting the capital letter, checks his voicemail, his email. Sherlock has floated behind his desk, by his portrait of the Queen. Mycroft can't see her, but he is hyperaware of her presence; he thinks she is standing with her hands clasped behind her back, studying the painting.

Just as he sets his phone down and recalls the speech he'd been prepared to give her (one she would no doubt divert, but he has another speech planned for that as well), she speaks.

"It's a fake."

Mycroft steeples his fingers and peers at them. "I beg your pardon?"

"A fake. It's well done. I'd thought you'd known, but I see you didn't, keeping it in such pristine condition. And the frame, too expensive for you to use on a replica." She steps around his chair, high heels surprisingly loud even against the carpet, and leans against the side of his desk, a smirk twisting her lips. "I suggest you have words with whoever procured it for you."

Mycroft smiles without showing his teeth, and says, "I'm well aware it's a fabrication, my dear sister. The frame is to lend credence to the illusion."

Sherlock snorts, looks away, disdainful. "Of course. Why have the truth when you can have artifice?"

"You're hardly one to talk about artifice," he points out, waving a languid hand at her attire. "May I ask why you've decided to dress - " his mouth makes a moue of distaste, " - like this? Miniskirts really don't suit you."

"It's for a case." Now a malicious smile; he could have pinpointed the exact curvature of her lips, if asked. Sometimes she is so predictable. "But then, you wouldn't really know much about that. Legwork and all, not really your area. It shows. Have you considered a diet?"

Mycroft is ready with a riposte. "Perhaps you could tell me how _you_ stay so thin, though I'm not sure if the side effects of prolonged cocaine use appeal to me."

For a moment, Sherlock is motionless, pale eyes staring directly into his, calculating, deducing. Then she laughs, and says, disbelieving, "Is _that_ why you've cut me off? A little drug use?"

"Hardly a little," Mycroft says. His voice has gone flat, angry, not purposefully; he swiftly remodulates and continues, seemingly in tune with the arched mockery of their little games. "Is that why you've so kindly dropped by, to question me about where your money has fled to?"

Sherlock thins her lips, and at her sides, her loose, agile fingers stop their incessant drumming and form fists. "I need that money, Mycroft."

"What you need is time in a rehabilitation facility," he counters, "which I will gladly pay for, and once you're released you can have complete access to your bank account once more. Is that a deal?"

" _No_ ," Sherlock hisses, and whirls on him, smacking her hands flat against his desk, bending until she can shove her face in his line of sight. "No, Mycroft, that is not acceptable, it's - you don't understand, I _require_ it to do my work - "

Sherlock in a rage is terrifying to some, intoxicating to others - Mycroft will admit, he used to fall in the latter group - but he is mostly inured to it. This, however, isn't a rage. This is desperation. It startles him, makes him sink a little further into his chair, but most of all, it wounds him. Sherlock is brilliant, of an equal to him, and to think she imagines that clouding her mind with foreign chemicals (benzoylmethylecgonine, sodium bicarbonate, and on and on, a list his mind can't stop quoting) is absolute anathema to Mycroft. And this makes him do something very, very stupid.

"If you require it, you're most certainly an addict," he says. "Without rehab, you won't be seeing any of your money, your PI business notwithstanding."

Too condescending, too blunt, and an ultimatum, something Sherlock does not take kindly to. Mycroft has miscalculated; he can tell by the way Sherlock slumps, minutely (sober, she would never let her guard down like that), then straightens. For a moment she's standing stiff and thoughtful - Mycroft, hands gripping the armrests of his chair, declines to speak, allowing her to respond on her own time - then she goes loose, lets her head loll back, and says, as if the words are just now occurring to her, "I suppose I'll have to find a new way to pay for my habits, then."

"Dealing drugs is a lucrative profession," Mycroft says carefully, "but hardly a good one in the long term. Thinking of brewing them at home, are you?"

Her eyes narrow, consideringly, but he can see her throw the idea away almost immediately. "No. I have sufficient knowledge of chemistry to do it, of course, but - " she shrugs, and the thin strap of her dress slips off her shoulder. "Impractical. It takes too long."

"Then what - ?"

Mycroft raises an eyebrow when she slides to perch on his desk directly in front of him, elbows on knees (her dress so scant it's barely deserving of the term), hands dangling. Thrown off balance, he pointedly keeps his eyes on her face. Her expression is cold, calculating, mouth parted in thought. She has lipstick on her teeth.

"I'm young," she says finally, having made her deduction. "Female. Not unattractive, if appealing mainly to a certain type of man - " (This Mycroft is certain of, having quietly taken out a fair number of would-be dominants and hopeful potential slaves fixated on his too-pale, too-inquisitive sister.) " - and of course, it's no matter to dress the part. How much could I ask, you think? One hundred pounds? Two? Five?" Her eyes drop to his, her mouth warped into that cruel little smirk again.

"I wouldn't know," Mycroft says after a long moment. "I think you would make an astoundingly terrible prostitute, my dear. Your feminine accoutrements, beguiling though they may be, are rather... _wrong_ on you."

He does not mean to be so inarticulate, but he is fascinated by Sherlock, how, as he says those words, she drops so seamlessly into the role she intends to play: she quickly loses the conniving expression and casual, almost mannish posture, eyes shuttering to half-mast, lips parting with the tip of her tongue peeking out at the corner; her hair, which had seemed windblown before, now looks mussed by passionate hands. Lounging on his desk, languorous, she is suddenly not his sister, his Sherlock, and is someone else entirely. Mycroft is impressed.

"Very nicely done," he says. Unthinkingly, he moistens his lips. "I'll have to reevaluate my previous statement."

"Will you now?" Sherlock purrs, and sets her feet in his lap.

Mycroft looks down. His breath has temporarily stilled in his lungs (again, startled, he presumes; she's doing that to him far too much today), and he examines the shoes. Dark blue suede, open-toed, an infinitely high heel; a designer label, Cavalli at a guess, more likely Emilio Pucci. They seem formed solely of a multitude of straps, the topmost encircling her ankle. The only thing about them remotely like Sherlock is the zip closure at the back, silver, sharp, and slightly out of place. Glancing up at his sister, who is smiling down at him (a close-mouthed, vampish smile), he hesitates; there are two likely directions for this to go. One, which Sherlock would expect, would be to stop this here, stand up, perhaps, or push her feet off his lap, tell her again that she will either go to rehab or he will force her there. The second option, though. Mycroft knows there are thousands of boundaries, thousands of lines to cross, and in his climb to his current position he has violated almost all of them. In order to succeed, he must first transgress; it's a cardinal rule of politics. So.

Mycroft places his hand on Sherlock's slender ankle, strokes her Achilles' tendon with his thumb. Her muscle twitches under his touch, and he travels higher, following the curve of her calf, brushing against the tender spot at the back of her knee, traces down the sharp line of her shin. Conversationally, he says, "Yes, your presentation is very convincing. I'm not certain you can go through with it, however."

He looks up, and Sherlock is only half in character, head tilted back slightly, luxuriating in his touch (a necessary part of human interaction, even for self-diagnosed sociopaths, and how long has it been since Sherlock had had contact with someone other than incidental brushes with strangers?). Her eyes fix on his, grey and chilly, and she asks with a lopsided smile that is only half a smirk, "Is that a challenge, brother mine?"

"If you make it one, sister dear."

And at that she slips off his desk, pours herself into his lap; for a moment she's just too much, limbs too long and hair too wild and Mycroft keeps his hands to himself, waits for her to adjust. She's never done this before, any sexual encounters she's had were no doubt short and clinical, light on pleasure. For once, Mycroft has the benefit of experience.

She wraps a hand around the back of his neck and presses her forehead against his; for a moment, her eyes slip shut, and when they open, Mycroft can see how a man would think the dilation of her pupils was from arousal, not cocaine. He touches her back lightly, cold skin bared by her dress, and draws his fingers down her spine; she shivers, and arches against him.

"I should point out that we are related, and this is distinctly taboo," she says, and Mycroft notes her voice is pleasantly husky, although whether that is artifice or natural he can't tell. "But I'm sure you haven't forgotten."

"Hardly," Mycroft tells her, and places his hand flat against the small of her back, his index and middle finger edging under the fine silk of her dress. "To be fair, you seem only half Sherlock at the moment. You are quite the actress."

"I know," she says smugly, and Mycroft cups her breast, brushing his thumb along her areola, a fleeting touch to her nipple through the silk. "Oh - " and she exhales, readjusts, wriggles nearer (which makes the baser parts of Mycroft's brain rapidly forget this is a game), and takes his wrist awkwardly, pressing his hand to her chest again. "Again, harder this time."

He's tempted to tease, ignore her wishes, but instead he rubs her nipple in slow circles, feeling it harden under his thumb; she squirms a little - she must be fantastically sensitive - and Sherlock sighs another _oh_ of surprise and says, breathily, "That - is interesting."

He peers at her, and the light in her eyes is one of discovery. Repeat the experiment, his mind says, and he does, just to see Sherlock reassert herself over the seductress she so successfully played, and she says again, "Interesting. I didn't expect to - respond like this, not to _you._ "

"Flattering. Thank you." Perhaps seeing her shed the role that set her apart from the one coded Sherlock, sister, should make him hesitate, or take a more clinical delight out of touching her, allowing his hands to explore, watching her responses, but it only increases his fascination.

"Have you done this before?" he inquires, curious, before dropping his mouth to her neck. She usually keeps her hair up, tied away from this spot, claiming it's irritating to leave it down; logically, she should be very sensitive there. He's rewarded by the slightest of moans, and introduces teeth. Her hips lurch in response, grinding against him (and he's hard, of course; a lapful of Sherlock would leave anyone thus indisposed).

" _Mycroft_ ," she says, rather stunned by how her body betrays her, and when he laves the spot with his tongue, she grips the lapels of his jacket tight. After a moment, where Mycroft pauses to let her regain control, she swallows and says, her tone a curious mix of intrigue and affront, "Of course I have; I did go to university, after all. It was the logical thing to do, to experiment."

Mycroft makes a noise of agreement - that _is_ what university is for, after all; where else would he have practiced all that he's putting to good use now? - and runs his hand up her thigh to where it meets the curve of her buttocks, covered by lace knickers, undoubtedly sheer, exactly what the girl who'd wear this outfit would have on under her scandalously short dress. For a moment, he basks in the thought that he is successfully rendering Sherlock speechless, of making her composure crack - but then she trails a hand down his chest, palms him through his trousers, and Mycroft cannot help but make a noise in response. Her head is buried against his shoulder, and when she speaks it's muffled, if curious.

"This, though, is different," and she makes as if to unbutton his trousers. He stops her moving hands, and she raises her head to look at him. "Oh, don't start," she says nastily, apparently in regard to his expression. "Yes, I've primarily experimented with females. That doesn't mean that men haven't caught my eye as well. Bisexuality exists, Mycroft, and sexuality is far more fluid than most would - "

Mycroft, frankly, doesn't care. There are countless articles in countless scientific journals he could read to substantiate her point, were he unaware of it, but as it is, he'd rather she stop condescending and touch him again. He takes her chin in his hand and kisses her, stalling the lecture, and though Sherlock is momentarily still against his lips she soon opens her mouth to him and presses her entire body against his - the points of her stilettos are digging into his thighs, but Mycroft doesn't want her to move; he wants her to stay here, warm and pliant under his hands in a way Sherlock never was before, with her mouth open and lipstick smeared, wet enough to have soaked the cotton lining of her knickers when Mycroft brushes his knuckles against her. He slips his fingers under the fabric and strokes against the wiry curls there, and Sherlock pulls away from the kiss, stares at him with wide eyes turned inward, cataloguing every sensation. It is the best thing Mycroft has seen in his life, the jolt of her body when he slides his thumb through her slickness to her clit, how her mouth forms a heart-shaped oh when he presses a finger inside of her, the cant of her hips as she tries to move with his hand and how she doesn't seem to be remotely aware of his existence - she is utterly entrancing, and he would be content if this were all, if this was the sole glimpse of her like this he'd ever see.

But she catches his wrist just as he's about to bring her off, knowing from the contractions of her muscles and the flutter of her eyelids how close she is, and looks at him with a gaze snapped back to total awareness. Under the full force of those eyes Mycroft would most likely do anything she asked of him, and he has to swiftly, harshly marshal himself into some semblance of control (losing the thread of the narrative is what kills lesser men in the political arena), even as she's opening his trousers, taking out his cock, the skitter of her fingers on his swollen flesh close to actual torture.

"Don't stop me," she warns, and rises onto her knees, that scrap of lace now dangling from her ankle. Mycroft holds her by the hips, under her dress, pressing palms to feverish skin, and when she sinks down on him Mycroft can't help but jerk her hips forward, forcing her to take him completely, and Sherlock cries out, a hoarse little yelp, and moves with him. She is almost too violent, but Mycroft does prefer his lovers to do the work and so lets her ride him, working toward her orgasm with frantic eyes. Mycroft cards his fingers through her sweat-soaked hair and summons up equations in his mind for a momentary distraction. He is a gentleman, after all. Of course, mathematics can only do so much, and after a few minutes Mycroft abandons those and focusses on Sherlock and the gleam of her skin and the rough, broken noises she's making into his shoulder - _exquisite._

When she comes it's with a series of shudders and her teeth digging in to the shoulder of his suit jacket; if she makes any noise, it's too quiet for him to hear. Immediately Mycroft stands, lifts her up and sets her on the desk, her limbs akimbo, still shaky and dazed post-orgasm; he braces himself with one hand and uses the other to finish, inhaling Sherlock's scent as he does. She helps him with the last few strokes, her palm more calloused than his, a few scars, the result of ignoring lab safety precautions, and he's looking into her face, her inquisitive expression when he spills over her hand with a grunt before stumbling back - yes, Mycroft _stumbles_ \- collapsing into his chair. Sherlock rubs his semen between her fingers, examines it in the light, tastes it - were Mycroft a younger man, that would be enough to get him going again - and finally rubs it off on her dress, her mind clearly moving to different topics.

By now, Mycroft has tucked himself in and made himself more or less presentable (unlike Sherlock, who looks thoroughly debauched), and has considered, cast aside, reconsidered what actions to take next, what reactions to make to her movements.

"I suppose you'll be canceling the appointment at the rehab centre," Sherlock says eventually. Incredibly smug.

"Actually, no," Mycroft says smoothly. His plan has obviously deviated from its course, but now they're on track once more. "I'll send a car for you on Thursday. Montague Street, correct?" As if he doesn't know.

She stares at him a moment, throat working in rage, and snaps, "Did you miss what just happened here, _brother mine?_ Or did you think you could - "

"Sherlock, think," he says patiently. He hates this, hates hurting her, but it's necessary for her survival; the part of him that cares is swiftly overcome by a rushing coldness, a coping mechanism of sorts, one he recognizes from his work. Transgressions, love, sex - they're all politics at heart. "It's the word of a sociopathic coke fiend against that of a high-ranking government employee. My poor little sister, throwing herself at me in a desperate attempt to gain the funds necessary to procure the drugs she's so terribly addicted to. Which of us would they believe?" A pause, a gesture at Sherlock's current state, mussed and sweaty with love bites bruised into her neck. "And you know how much _this_ would upset Mummy."

He stares her down, watches her jaw clench, watches her sweep her composure about her like a trench coat. Her eyes are not at all like ice; ice implies that the cold anger there is capable of melting.

"Very well," she bites out, then, "Blackmailer." She tarries a moment more, possibly casting about for a weapon (or waiting, unsure, uncertain - but no, that is impossible for Sherlock), then shoves the door open with a clatter.

Mycroft sits back in his chair, lowers his eyes to his documents as she stalks out of the room. He regrets it, truly he does, but this is for Sherlock's own good. He raises his fingers to his mouth, where her taste still lingers, and, dispassionate though he is, he understands the meaning of the metaphorical clenched heart.

He doubts she will ever stop hating him.


End file.
